LAS VEGAS (AP) - Ronda Rousey heard the chorus of boos again. This time it was for a different reason.

Rousey kept her UFC women's bantamweight title, dropping Sara McMann to the mat with a left knee to the area of her liver at 1:06 of the first round at UFC 170 on Saturday night.

Rousey (9-0) was booed by fans during the post-fight interview after the co-main event was quickly stopped by referee Herb Dean, much to the fans' dismay at Mandalay Bay Events Center. McMann, who seemed hurt after the blow to her right side with her back to the fence, is now 7-1.

''I didn't think it was too soon,'' Rousey said. ''Obviously, that's why we have a referee in there. I just went to that spot.''

The 27-year old from Venice, Calif., is 9-0 after a quick battle Saturday and trip back in the octagon after defeating Miesha Tate on Dec. 28.

''I told (UFC President) Dana (White) I will fight on 24 hours' notice,'' Rousey said. ''I know we spent a lot of time training in the clinch. We were focusing on the knees. I'm still learning. I was doing the judo when I was kid. I feel I'm more rounded as a martial artist now.''

Rousey, who was a 4-1 favorite, was also booed after her last title defense against Miesha Tate. Rousey refused to shake hands with Tate after their bout at UFC 168 in December.

Both fighters started Saturday night's fight with a flourish before Rousey backed McMann, a 33-year old from Gaffney, S.C., to the fence. After the liver shot, McMann did not fight back and Rousey used a left shot to the same area.

''Looking back, it seem kind of quick,'' McMann said. ''I should get up quicker. If you want to win fights, you have to get up quicker. When I hit the ground, I got my bearings back. When I heard his voice, I was reaching for a leg.''

McMann only landed one good shot on Rousey.

In the other co-main event, Daniel Cormier (13-0) easily defeated Patrick Cummins (4-1) by TKO at 1:19 of the first round of their light heavyweight co-main event.

Cormier, who just moved down a weight class, hit Cummins with a right upper cut and knocked him to the mat. Cormier never recovered.

''It feels good because it was my first finish in UFC,'' Cormier said. ''Training camp was long and hard and I prepared for a long fight, but I have no complaints. I've been talking about this move (to light heavyweight) and when you do it the right way, you don't feel any effects. At heavyweight, I could feel these guys out. I think these guys (at light heavyweight) are a little faster.''

Cummins, a 9-1 underdog, lost his job at an Orange County coffee shop for taking White's phone call to fight on Saturday, filling in for Rashad Evans, who blew out his knee in training. White said Cummins would have another fight ''to prepare for,'' and would use him again.

The card also featured three welterweight matches.

Canadian Rory MacDonald got past Brazilian Demian Maia by a unanimous decision with all the judges scoring it 29-28 in the three-round final welterweight bout. Maia (18-6), a 2-1 underdog, had MacDonald (16-2) on the mat most of the first round and later had a takedown midway through the third. But MacDonald later escaped about a minute later in the third.

Stephen Thompson knocked out Robert Whittaker in the first round of the main card's first match. Thompson (9-1) used two rights to the left side of a stumbling Whittaker (12-4), who later went down. Whittaker then landed a barrage of punches as the fight was stopped at 3:43.

Mike Pyle defeated TJ Waldburger by technical knockout in the third round at 4:03 of the second welterweight bout of the night. Pyle (26-9-1) dominated Waldburger (16-9) in the first two rounds.

But the night belonged to Rousey, who is filming a movie in March.

''I promise my coaches I would drop her with a body shot,'' she said. ''It was a goal I had for this fight. I'm happy I did that for them tonight.''